Refrigerant handling systems such as a refrigerant recovery, recycling and recharging unit have internal scales that are used, among other things, to weigh a storage tank containing refrigerant. One way to test the scale to ensure it is calibrated is to use a weight having a known weight. To determine if a scale is calibrated, a user puts the calibrated weight on the scale and compares the reading of the scale with the known weight. The weight is typically attached to auxiliary hardware such as hooks or baskets and thus may introduce potential errors. Additionally, the refrigerant tank typically sits on the scale and is secured to a housing of the unit. In order to test the calibration of the scale, the unit must be dismantled and the tank must be removed thereby taking up valuable time that could be used to otherwise service a vehicle.
In addition to providing good operation of a fluid handling system, calibration of an internal scale may also be required by industry standards. For example, SAE J-2788 requires that certain refrigerant handling systems include a means for the user to verify that an internal scale is calibrated.
Accordingly, it is desirable to provide a method and apparatus that in some embodiments of the invention, permit a user to determine whether an internal scale for a refrigerant handling system is calibrated.